My m5 has just started making a rattling tapping noise which is present from start up.

When the engine is idling the rattling seems to come and go and the engine is down on power there's no warning lights and I've always maintained a service schedule.

Any ideas on what it could be please?

Mali, October 2014

I'd suspect the timing chain. Friend of mine had his break, which resulted in a very large repair bill.

ChicksFan, October 2014